Tubular lamp filament support



July 13, 1965 s. G. REIDENBACH 3,195,000

TUBULAR LAMP FILAMENT SUPIORT Filed Oct. 28, 1963 l lnvenlror1 2 S iranbeg (a. Reidenbach by an: f

His Adr to neg United States Patent 3 195,000 TUBULAR LAMP FILAMENT SUPPORT Stanley G. Reidenbach, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Filed Oct. 28, 1963, Ser. No. 319,214 3 Claims. (Cl. 313-271) This invention relates generally to electric incandescent lamps, and more particularly to tubular lamps having an axially extending coiled filament. Still more particularly, the invention relates to filament supports for lamps having coiled coil filaments, i.e., filaments formed by winding the filament wire to form a helical primary coil which is again helically coiled to form the secondary coil of the coiled coil filament.

In tubular lamps of the double ended type having an axially extending filament connected at its ends to leadin conductors sealed through opposite ends of the envelope, it has been the practice to provide auxiliary support members at one or more locations on the filament intermediate its ends, to support the filament from the envelope walls and maintain it generally at the axis of the envelope. For a filament in the form of a simple helical coil, a widely used form of support comprises a wire member having one end coiled around the exterior of several turns of the helical filament coil and extending therefrom, usually in the general form of a spiral, to be circumferentially engageable with the inner wall of the envelope. However, such a support is not suitable for coiled coil filaments, particularly filaments of high wattage and therefore relatively large size. Previous attempts to provide a suitable support for coiled coil filament lamps have suffered from various disadvantages such as failure to firmly support the filament in the axis of the envelope, difficulty in making the support and assembling it with the other lamp components, and electrical short circuiting of portions of the filaments in varying degrees, or requiring additions to the length of the filament thereby nullifying, to some degree, the desirable compactness of a coiled coil filament.

It is therefore an object of the invention to provide a support structure which will obviate the above-stated disadvantages to provide a support member of relatively simple design and ease of assembly and which will firmly support the coiled coil filament in the axis of the envelope.

Briefly stated, and in accordance with one aspect of the invention, the coiled coil filament is interrupted or separated at a point intermediate its ends to define separate sections or segments, and the adjacent interrupted ends joined by a support member comprising a wire portion which is formed to conform to at least a portion of a turn of the secondary coiling of the filament and which is fitted as a mandrel or core in the interior of the primary coiling of respective interrupted adjacent ends of the coiled coil filament sections. Additional portions of the support member are formed to support the said mandrel wire portion from the inner Wall of the lamp envelope.

Further features and advantages of the invention will appear from the following detailed description of species thereof, and from the drawing wherein:

FIG. 1 is a perspective view of a lamp having a filament support in accordance with the invention;

FIG. 2 is a transverse sectional view of the lamp;

FIG. 3 is a perspective view of the filament support and adjacent end portions of the filament segments; and

FIG. 4 is a transverse sectional view of the lamp showing a modified support structure.

Referring to FIG. 1 of the drawing, the lamp illustrated therein comprises a tubular envelope 1 of vitreous material having compressed pinch seals 2 at its op- 3,195fififi Patented July 13, 1965 posite ends through which extend lead-in conductors 3 having their inner ends connected to respective ends of a coiled coil filament 4 which extends axially of the envelope. The lamp may be of the so-called iodine cycle type wherein the filament 4 is of tungsten wire and the envelope 1 contains a quantity of iodine which functions as a regenerative getter to return to the filament 4 tungsten which is vaporized therefrom during operation of the lamp, as described and claimed in Patent 2,883,571, Fridrich and Wiley. The envelope 1 preferably also contains a filling of inert gas such as nitrogen, argon, krypton or xenon at substantial pressure preferably exceeding atmospheric. Since the envelope of such a lamp attains elevated temperatures exceeding 250 C., it is preferably made of glass of relatively high melting point such as borosilicate or alumino-silicate or quartz glass. Each of the lead wires 3 includes an intermediate foil portion 5, preferably of molybdenum, which is hermetically sealed in the pinch seal 3, an outer portion 6, preferably of molybdenum, and an inner portion 7, preferably of tungsten and which is connected to the adjacent end of the filament 4 in any suitable manner.

In order to support the filament 4 in the axis of the envelope, auxiliary support means are provided, in this case a single support member at the midpoint of the filament. For the purpose, and in accordance with the invention, the filament 4 is interrupted or separated at its midpoint to define separate sections or segments 4a and 4b which are joined at their adjacent interrupted ends by a support member 8.

The support member comprises a helically coiled wire portion 9, preferably of not more than one turn of a helix, and of a coil diameter and pitch corresponding substantially to the coil diameter and pitch of the secondary coiling of the coiled coil filament 4, and fitted as a mandrel or core in the primary coiling of respective interrupted adjacent ends of the filament sections 4a and 4b, as shown more clearly in FIG. 3. The said helically coiled portion 9 thereby interconnects the separated ends of the filament both mechanically and electrically.

The said helically coiled support portion 9 is suitably supported from the envelope wall. As shown in FIGS. 1 to 3 this may be done by a wire portion having a straight leg section 10 which is suitably connected at one end to the midpoint of the helically coiled portion 9, as by welding or by being tightly wrapped around it. The leg section 10 extends generally radially of the envelope cross section and terminates in a loop section 11 which extends around at least half the circumference of the inner envelope wall to be in engagement therewith and thereby support the helically coiled portion 9, and the filament 4, in the axis of the envelope.

As illustrated in FIG. 4, the loop section 11 of the support member of FIGS. 1 to 3 is eliminated and the leg section 10a is extended and is sealed in the residue 12 of an exhaust tubing used in evacuating and gas filling the envelope.

It will be evident that a similar anchoring effect may be achieved with the structure of FIGS. 1 to 3 by providing a laterally offset leg on the end of the loop 11 and which extends into the exhaust tip 12.

It will be seen that the helically coiled support portion 9 fits snugly into the primary coiling of the coiled coil filament 4 without changing the filament configuration, and that it supports the filament accurately in the envelope axis and short circuits a definite short length of primary coiling of the filament.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric lamp comprising a tubular envelope containing an axially extending helically coiled coil filament, said filament being interrupted at a point intermediate its ends thereby defining separate filament segments, and a support member joining the interrupted adjacent ends of said filament segments and supporting them from the envelope Wall, said support member comprising a helically coiled Wire portion of a coil diameter and pitch corresponding substantially to the diameter and pitch of the secondary coiling of said coiled coil filament;

and helically coiled wire portion having portions thereof fitted as a mandrel in the primary coiling of respective interrupted adjacent ends of said filament sections and thereby interconnecting them, and another portion of said support member secured to said helically coiled Wire portion at a location intermediate its ends and between the terminal ends of said filament sections andsupporting said helically coiled wire portion from the wall of said No references cited.

DAVID J. GALVIN, Primary Examiner. 

1. IN AN ELECTRIC LAMP COMPRISING A TUBULAR ENVELOPE CONTAINING AN AXIALLY EXTENDING HELICALLY COILED COIL FILAMENT, SAID FILAMENT BEING INTERRUPTED AT A POINT INTERMEDIATE ITS ENDS THEREBY DEFINING SEPARATE FILAMENT SEGMENTS, AND A SUPPORT MEMBER JOINING THE INTERRUPTED ADJACENT ENDS OF SAID FILAMENT SEGMENTS AND SUPPORTING THEM FROM THE ENVELOPE WALL, SAID SUPPORT MEMBER COMPRISING A HELICALLY COILED WIRE PORTION OF A COIL DIAMETER AND PITCH CORRESPONDING SUBSTANTIALLY TO THE DIAMETER AND PITCH OF THE SECONDARY COILING OF SAID COILED COIL FILAMENT, AND HELICALLY COILED WIRE PORTION HAVING PORTIONS THEREOF FITTED AS A MANDREL IN THE PRIMARY COILING OF RESPECTIVE INTERRUPTED ADJACENT ENDS OF SAID FILAMENT SECTIONS AND THEREBY INTERCONNECTING THEM, AND ANOTHER PORTION OF SAID SUPPORT MEMBER SECURED TO SAID HELICALLY COILED WIRE PORTION AT A LOCATION INTERMEDIATE ITS ENDS AND BETWEEN THE TERMINAL ENDS OF SAID FILAMENT SECTIONS AND SUPPORTING SAID HELICALLY COILED WIRE PORTION FROM THE WALL OF SAID ENVELOPE WITH ITS AXIS SUBSTANTIALLY COINCIDENT WITH THE ENVELOPE AXIS. 